## update plt_fn version
- prev_fn : <name_fn>v<current>_
- upd_fn : <name_fn>v<current+1>_
- in .frc/a : _name_fn="prev_fn"
  - warning in any code exec : prev_fn -> ${_name_fn}
- cr <name_fn>v<current+1>_
  - if mast backward compatibility : ifs_prev_fn identicaly ifs_upd_fn
    - if add props to upd_fn : tst new props
- in .frc/a : _name_fn="upd_fn"
